flocking your ota

monoxide · #1 25-09-2007, 10:47 PM

hey guys,

i've been wanting to flock my 12" tube and thought those a4 sheets of sticky back felt would be the way to go but found they were a little bit more pricey than i expected...
from spotlight here they were ~$2.50 per sheet which didn't sound like much until you realise how many you need for a 12" tube.

right now im sitting on the fence thinking that if its not a great improvement the money may be better spent somewhere else.

anyone that has flocked their tube, id love to hear how you did it and how much improvement there was.

davewaldo · #2 25-09-2007, 11:03 PM

Hi TJ!

I was thinking at one stage of flocking my tube, the GSO tubes are well known for being grey rather than black. I looked at various methods, but in the end I decided that high quality black paint was the way to go. I found that felt gathers, and deposits dust which is bad for obvious reasons. Velvet could be good but is hard to apply and also expensive (and has dust issues). I also thought it could be messy when these fabrics become damp from dew.

I used Krylon ultra flat black, which is rumored to be the same paint used by Meade (although thats not why I used it). Several other IISers recommended it to me. 2 cans was enough for my 10" tube and the results are great. Much darker than the stock paint.

Many users apply a texture paint first, and then the black on top to aid in light adsorption.

If you do a search for flocking on here you will have hours of reading to trawl through. One of the threads also gives the paint number for the Krylon paint.

hope this helps,

Dave.

monoxide · #3 25-09-2007, 11:24 PM

thanks Dave,

why didnt i think of searching...

the inside of my tube looks more like a cross between matte and gloss, i gave the tube a clean out today while i had the primary and secondary out and you can clearly see its changed the finish on the paint.

i guess i just assumed that felt or similar would be better than a paint

the dust isn't a big concern for me as i regularly have to clean my mirrors anyway, since i live near the sea its a really bad idea to leave any dust on the mirrors for too long or it will just eat right through the coatings.

Tannehill · #4 26-09-2007, 12:04 AM

I have a GSO dob and I hear ya. I flocked mine, but....

You don't really need to flock your entire tube. 95% or more of the benefit of flocking comes from blocking stray light from what you see from the focuser drawtube, looking thru the with the turned down focuser and stretching to see where any stray light can enter the bottom of the drawtube.

Two articles from S&T - one by Gary Seronik in S&T April 2001 in particular - illustrate this really well. PM me if you don't have access to this article, I can get the key information to you.

After some trials with various lines of flat back paint (altho not the Krylon mentioned here) I would say that flocking material is measurable superior to any paint I used. That's just my experience,

If you do apply flocking, apply it in slightly overlapping strips running down the tube's long axis, no more than 5 cm wide, and use high-tack (very sticky) adhesive type if such is available. (Protostar sells some great hi-tack variety that I used http://www.fpi-protostar.com/flock.htm) Otherwise, if you apply in one large sheet, when you are out and your metal tube contracts a bit, it'll peel off in giant spots and leave you with a mess!

I used scraps left over from a prior flock of an 18" dob for my GSO, pic below, and you can really tell the difference looking in the focuser afterwards. It's pitch black around the secondary now, whereas before you could see the "bright" (brighter) grey flat paint reflecting stray light off the tube into the focuser. You don't need to be "clean". Any untidy looking effects of patching on strips (as I did, having no large pieced left!) makes NO difference in performance.

Regards,

monoxide · #5 26-09-2007, 12:30 AM

Quote:

Originally Posted by Tannehill

I have a GSO dob and I hear ya. I flocked mine, but....

You don't really need to flock your entire tube. 95% or more of the benefit of flocking comes from blocking stray light from what you see from the focuser drawtube, looking thru the with the turned down focuser and stretching to see where any stray light can enter the bottom of the drawtube.

i thought that too, and i wasnt sure if i wanted to buy $100 of sticky back felt and do the whole lot before really looking into it so i got 1 square for behind the secondary, i put that piece in while i was cleaning the mirrors, it actually stuck really nicely and looks good but its cloudy here tonight so i didn't get to see if it made a difference.

Tannehill · #6 26-09-2007, 12:43 AM

Cool. It makes a huge diff for me with streetlights surrounding me. at a dark site, can't say as i haven't been as easily convinced of the pros. I think the flocked lip extending beyond the far end of the tube helps as much as the tube flock, to block stray light from lights from my suburb rooftop...

s

Quote:

Originally Posted by monoxide

i thought that too, and i wasnt sure if i wanted to buy $100 of sticky back felt and do the whole lot before really looking into it so i got 1 square for behind the secondary, i put that piece in while i was cleaning the mirrors, it actually stuck really nicely and looks good but its cloudy here tonight so i didn't get to see if it made a difference.